By Nat Shirley

Monday, Dec 31st, 2012 @ 3:10 pm

The Environmental Protection Agency has released its official fuel economy ratings for Ford's second plug-in hybrid, the 2013 Fusion Energi.

Like the C-MAX Energi with which it shares a powertrain, the Fusion Energi is certified at 108 MPGe (miles per gallon equivalent) in the city, 92 MPGe on the highway and 100 MPGe combined. Those numbers are good enough to top rivals such as the Chevrolet Volt (98 MPGe combined) and Toyota Prius Plug-In (95 MPGe combined) and quality the Energi as the most efficient sedan in the United States.

Helping the Fusion Energi to achieve its impressive mileage figures is an Atkinson-cycle 2.0-liter four-cylinder that teams with an electric motor and a continuously variable transmission. The setup is good for 188 horsepower, and, thanks to a 7.6-kWh lithium ion battery, an all-electric range of about 20 miles.

When it launches, the Fusion Energi may be thrust into the controversy that's currently raging over the accuracy of Ford's fuel economy claims for its non plug-in C-MAX and Fusion Hybrid models - which share the majority of their powertrains with the Energi. However, despite the disputed efficiency numbers, Ford's hybrids have been selling well - the C-MAX sold 8,030 units in October and November, making it the fastest-selling hybrid at launch - so the Blue Oval likely has high hopes for its plug-in sedan.

The Fusion Energi will hit the market in January with a base price of $39,495, although a federal tax credit is expected to shave $4,000 from its purchase price.